Insurance ratings for a vehicle may be based, in part, on the extent of damage, ease of repair of damaged parts, and repair cost of a vehicle in low speed impact events. One such event is the 15 kph, 100° angled, 40% offset, rigid barrier impact to the rear of the vehicle. In this impact mode, damage to the frame rail, back-light panels, rear floor panel, lift-gate, or deck-lid is undesirable. All these parts are welded together in a uni-body vehicle structure. Repair of these parts involves expensive procedures and may result in unfavorable insurance ratings. Unfavorable insurance ratings are a disadvantage when selling vehicles to customers. It is desirable to contain the damage only to fascia and bumper system assembly that can easily be unbolted from the main vehicle body and replaced after appropriate repairs.
Conventional bumper systems may include a bumper beam with reinforcements, the crush-cans (welded to the bumper beam), and the mounting plate (welded to the crush-can and bolted to the vehicle body). When the bumper system is damaged in a low speed impact, the bumper system is unbolted at the mounting plate and is bolted back on the vehicle after repair.
In a conventional bumper system, the crush-can and bumper beam are designed to avoid damage to the frame rail by avoiding the transfer of high loads to the frame rail. Frame rail damage is avoided by attaching a rail collar reinforcement around the frame rail. Crush space provided by the crush-cans is intended to limit the extent of damage to rear vehicle structures such as a lift-gate or deck-lid. A mounting plate is provided to secure the crush-cans to the frame rail to limit excessive displacement that may be caused by the in-coming barrier. The mounting plate is required to be relatively stiff to avoid deformation of the mounting plate that otherwise may result in damaging the back-light panels and the rear floor pan. Reinforcements are required inside the back-light structure to avoid damage to the back-light. A mounting plate, rail-collar reinforcement, and backlight reinforcement structure are necessary features in conventional bumper systems.
Large vehicles and SUVs frequently include an optional trailer-hitch for towing. The trailer-hitch system is bolted directly to the rails instead of attaching to the bumper system. Bolt access holes and additional reinforcements to the frame rail are required to accommodate the optional trailer hitch system.
Substantial weight savings may be achieved by eliminating the mounting plate, the frame rail-collar, the reinforcement to the lower back-light structure, and the additional reinforcement to the rail for the trailer-hitch system. It would also be advantageous to have a single design for the frame rail for vehicles that either include or do not include the optional towing package.
The above problems and other problems are addressed by this disclosure as summarized below.